Spine Surgery

Spine surgery is rarely an initial treatment for back pain. Spinal fusion surgery comes in many forms: Lumbar spinal fusion, cervical spinal fusion. They are all designed to help limit pain caused by the joints. Low back pain (pain in your lumbar spine) is the most common. Most back pain comes from sprains and strains caused by stressful movements, for example: lifting something without using proper techniques or a sudden twisting motion.

Spinal Fixation

What is the Reason for Spinal Fixation?

Where your spine, for whatever reason, has too much movement or is not sufficiently stable by itself to support the necessary stresses and strains that tend to be put on it on a daily basis, then spinal fixation is often the answer. People who suffer considerable pain on movement, or when they experience tingling in an arm or a leg might be considered for spinal fixation if the cause is due to movement in the spine putting pressure on one of the nerves. Furthermore, if a person experiences numbness or weakness in an arm or leg this could be due to spinal compression, with the bones in the spine pressing on an adjacent nerve. Spinal fixation will fuse the bone in the area that is causing the problem, making a more rigid support that is also more stable.

How Did Spinal Fixation Develop?

Setting broken bones, in the past, involved the use of plaster casts made from plaster of Paris, to hold the bones in one place to enable healing. If bones move around too much when they need to heal, the cells involved in the process of healing will not be able to complete their job properly and the broken bones will heal badly, if at all. More recently, internal fixation has become the norm, using screws and plates to hold damaged bones together. The rigidity of the metal plates provides the necessary support that prevents movement as the bones knit together. There are many fractures that actually respond better to internal fixation, as well as being more comfortable for the patient.

Spinal support was largely reliant on external fixation and, in some cases, still is. However, internal metal plates, rods and screws are increasingly taking the place of what many people view as barbaric-looking external fixation devices. Support within the body has a number of advantages which are discussed in more detail later. Largely, however, a more rigid structure is achieved with internal fixation allowing for enhanced healing. Greater support is achieved enabling the patient to mobilize much more quickly after surgery, thereby reducing the chance of DVT and embolisms developing through sluggish blood flow. Patients are often able to return to their normal daily activities within 6 weeks of surgery, including a return to work in most cases, which has a far greater psychological and sociological outcome for all concerned.

Anatomy and Physiology of the Spine

The musculoskeletal system of the spinal area is quite complex so it is hardly surprising there are so many things that can go wrong with it. Two of the most common kinds of pain you can experience are from pain in the neck and pain in the lower back but, because of the sheer complexity of the anatomy and physiology of the spine any pain you experience in any areas of your spine could be caused by a range of conditions making these kinds of problems quite difficult for clinicians to diagnose, especially if the pain emanates from one of the facet joints. This condition causes chronic pain and, on the occasion it is diagnosed correctly, is known as Facet Syndrome, or Facet Joint pain.

Distinct Divisions of the Spine

The spine is made up of a series of very distinct areas, each containing a number of individual bones. Each section has a slightly different function although, overall, the spine is intended to provide support for your muscles and tendons and to provide protection for the spinal cord. The bones that make up the spine are each called vertebra, with 33 vertebrae making up the whole length of the vertebral column. The spine is divided up into:

Cervical vertebrae – 7 bones

Thoracic vertebrae – 12 bones

Lumbar vertebrae – 5 bones

Sacrum: these are fused vertebrae, consisting of 5 bones

Coccyx: this is the vestigial tailbones, consisting of 4 very small bones

Cervical Vertebrae

These tend to be labeled C1 – C7 and are responsible for the movement of the neck as well as providing protection for the top of the spinal cord together with other nerves and arteries that, in this area, are quite major as they extend into the skull and connect the brain with the rest of the body.

Thoracic Vertebrae

The 12 vertebrae making up the thoracic vertebrae are referred to as T1 – T12. These are the vertebrae that form the back of the rib cage.

Lumbar Vertebrae

The lumbar vertebrae are often referred to as the ‘small of the back’. They consist of 5 bones, referred to as L1 – L5. This is a very common area to experience back pain as the lumbar region takes considerable stress from the amount of weight placed on it.

Sacral Vertebrae and Coccyx

Together these consist of 9 bones, all of which are fused together in adulthood. The sacrum is generally referred to as S1 and consists of a single unit of bone.

Inter-vertebral Discs

These discs intersperse the above bones of the vertebral column.

Each one is a flexible cushion of tough, cartilaginous material that prevents friction between the bones and provides protection against potentially damaging jarring when moving. The shock absorbing qualities of each disc is achieved through the nucleus pulposus, a spongy liquid that absorbs any shocks, each of which is surrounded by a tough fibrous membrane. In cases where discs herniated through this outer membrane this interior jelly can press against nerves in the spinal cord, causing severe pain. The vertebral bones are put together and tend to be the cause of many of our spinal problems, as well as fulfilling a very essential function within the body. Aside from protecting the spinal cord, the spine serves as a conduit through which all the major information from the brain reaches the network of muscles, nerves, bones, tendons and ligaments through which neural information is disseminated to every cell within the human body. In situations where illness or injury causes the spine’s function to be impaired, without active intervention the results could lead to chronic and debilitating pain as well as causing major disability.

Spinal Cord

The spinal cord runs through the vertebrae, from the base of the brain to the lower end of L1, lumbar vertebra. The cord itself is protected, not just by the overarching bones of the vertebral bones, but by a particularly tough membrane known as dura mater. This completely encloses the spinal cord within a waterproof casing, within which is spinal fluid that helps to provide additional protection as a shock absorber for the spinal cord encased within. Each part of the body is joined to specific nerve roots that leave the spinal cord at certain points. The nerve roots in the cervical area of the spine provide neural support for a network of nerves over and around the arms and upper chest while the nerve root leaving the lumbar area supply nerve stimulus to the buttocks, hips and legs. If these nerves are damaged, or compressed, you will experience symptoms such as tingling, numbness, weakness or pain of varying degrees. This can be felt not just in the immediate vicinity of the injury, but as referred pain elsewhere in your body.

Muscles of the Spine

There are actually 7 layers of muscles that are responsible for moving the body and limbs around, each one of them surrounding the vertebral bones. As you can see from the diagram, they are responsible for maintaining an upright posture and being able to carry loads and undertake normal day to day activities. Damage to the spine can interfere with the activity of these muscles, causing weakening or even preventing movement from occurring with any ease.

Normal Spinal Curvature

If you look at a normal spine you will note that, when viewed from the front or the back, the spine appears to be a straight line. Should the spine appear to curve to either side when looked at from this view, it is indicative of scoliosis. In a normal spine, when looked at from the side, there are three gentle curves, two inward and one outwards. The cervical spine and the lumbar spine both exhibit an inward curve. This is medically referred to as a lordotic curve. Meanwhile, the thoracic spine curves outwards. This is known as a kyphotic curve. The way the spine curves is adequate to support the weight of the upper body and the head as well as to maintain a suitably upright balance. If curvature is too extreme the spine could become too imbalanced, causing pain and disability.

Vertebrae. These consist of pedicle supports which are bony parts that provide an arch of bone across the spinal cord. The back of this bony arch consists of the laminae.

Intervertebral Disc.

Facet Joint. This joint connects the bony arches together. Each pair of vertebra has two associated facet joints, one above and one below. The facet joint is a synovial joint that enables each vertebra to pivot around, enabling rotating movement to occur.

Neural Foramen. This is an opening beneath each vertebral arch that enables the nerve roots to leave the spine to join up with other parts of the body. Each pair of vertebrae are associated with two neural foramen. The function of the neural foramen is to protect the junction of the nerves where they join the central nervous system.

The spinal cord runs the length of the vertebral column and is protected along its length by the interlinking vertebrae, the pedicle arch and their associated facet joints. The spinal cord runs from the base of the brain to the end of the 1st lumbar vertebra, where L1 meets L2 after which it frays out into a number of lesser nerves, each one major in their own right. The medical term for this is cauda equina as its appearance is that of a horse’s tail.

When Things Go Wrong

This very complex system of our musculoskeletal framework, with its interspersed network of nerves can be the cause of things going wrong, often something quite small can send quite major signals of pain to the recipient. The nerve roots that leave the spinal cord are extremely sensitive, not just to alterations in posture or movement but to pain. Facet joints in the lumbar vertebrae are also particularly sensitive to pain so it is hardly surprising that so many people experience prolonged periods of incapacitation due to chronic pain in the lumbar region of the back.

When pain is experienced from subluxated facet joints or from impinged spinal nerves the muscles of the trunk are quick to respond. Muscles contract when the nerves supplying them are damaged in any way, resulting in muscular spasm which can be extremely painful. If any of the five sciatic nerves in the small of your back are impinged in any way you can experience a particularly painful condition known as sciatica. This often occurs if there is something pressing against any of these nerves. Apart from the pain, it can cause tingling and numbness in the gluteal muscle of the buttovcks and down both legs into feet and toes. If this continues, muscles can become weak and will eventually atrophy.

Imaging Tests

Accurate internal fixation has largely been achieved through the development of more accurate imaging techniques such as MRI scanning and bone scans using special dyes that show any boney defects in far greater detail than any X-ray could ever achieve by itself. There is still a place for X-rays, especially the various techniques associated with X-ray technology: X-ray is a far cheaper imaging technique than MRI or CT scans, for example. Diagnostic injections that insert a special dye into the body certainly produce far better results than what was available before these were sufficiently well developed to be of any use. Skilled clinicians trained in these new techniques have now come of age as well, with surgical training keeping pace with these new diagnostic tools. This ensures that surgeons are able to implement these technological advances while, at the same time, have the necessary skills to operate and use them to fix the spine more effectively.

Advances in Fixation Materials

Better rods and screws have certainly made a great difference to spinal fixation methods. A provisional patent was applied for in July 2008 for screws made from bio-absorbable material. This material combines the strength required for internal fixation with the advantages of not having metal encased within the body, especially relevant in terms of MRI testing, for one thing. One particular bio-absorbable screw for bone fixation has been awarded US patent number 5.470.334; others can be found under US patent number 4.968.317. Whether these bio-absorbable materials will completely replace the Kirschner apparatus that includes the various stainless steel pins and interconnecting rods used for internal fixation and the clamps, together with nuts, used for external fixation, remains to be seen.

When is a Spinal Fixation Necessary?

Surgery to correct spondylolisthesis, which results in spinal bones becoming unstable and pressing on major nerve groups, is one condition which often makes spinal fixation necessary. This condition often results in patients developing bone spurs and protrusions of spinal discs. These are usually moved away from the spinal cord and any nerve roots at the time of surgery. In order to do this, it is often necessary to remove these: this causes further de-stabilization of the bones in the spine, necessitating the use of rods and screws to prevent the bones from slipping any further.

Scoliosis: Scoliosis, which is when the spine bends into abnormal positions, is another condition that can be successfully corrected with the use of rods and screws. When scoliosis results in the spine curving too much for the patient to be comfortable, it often becomes necessary to insert rods to correct the spine’s continued curving.

Infections: Infections and tumors also often result in bones becoming unstable, making spinal fixation necessary while the patient has the underlying cause treated. Removing tumors from the spinal region can reduce pain caused by the developing tumor, while spinal fixation can help the patient remain mobile, reducing the possibility of DVT and other blood clots from developing as well as improving the patient’s psychological outlook, enabling them to better cope with their illness.

Fractures: Fractures need to be dealt with on an individual basis depending where they occur in the spine. Statistics report that as much as 90% of all spinal injuries occur in the thoracolumbar region of the spine. Out of these between 10% - 20% are burst fractures. These are fractures that occur as the result of vertical compression when the spine is slightly flexed. Burst fractures can also occur as the result of a rotational injury. These burst fractures have been described in terms of different mechanisms of injury that can become intensely complex and detailed. Suffice to say that any injury to the spine that results in bone fragments being propelled towards the spinal canal, or where the vertebral pedicles are fractured, are considered to be major burst fractures and the source of severe injury that needs some form of spinal fixation to prevent further damage.

Burst fractures in the thoracolumbar region can result in neurological damage whereas an effective repair can result in an opportunity to heal with few problems. Spinal instability was adequately defined by Nicoll in 1949. This definition was based on the degree of subluxation or dislocation and the degree of disruption to interspinal ligaments, including if relevant, laminar fractures of lumbar vertebrae, L4 or L5. This definition is so respected in surgical circles that, even after more than 50 years, Nicoll’s definition continues to be used in decisions of how to treat these fractures. A decision to undertake spinal fixation needs to take into account the degree of mechanical and neurological instability caused by the injury and considers how appropriate the spinal fixation would be in terms of recovery. Basically, however, spinal fixation is appropriate to repair mechanical instability due to vertebral collapse; neurological instability where spinal fixation can prevent further neurological injury; and a combination of the two. This is referred to as the 3-column model. Instability has been interpreted as:

50% of the vertebral height lost as the result of inter-disc compression

Furthermore, if a posterior longitudinal ligament injury was identified by MRI in conjunction with a burst fracture, this should be considered for spinal fixation. Another categorization of what is a stable or unstable spine is the AO/Magerl Classification that uses pathomorphological criteria together with three mechanisms of injury, the effect of which needs to be shown up on CT scans and radiographs. The results are categorized as being:

A: compression

B: distraction

C: rotation type fractures

Where the Spinal Canal has been Compromised

When the CT scan reveals a spinal canal has been reduced by 40% - 50% by thorocolumbar burst fractures many surgeons will carry out spinal fixation. Nevertheless, there is no guarantee that, by the time spinal fixation has been carried out, paralysis wouldn’t have occurred. Imaging appears to indicate that the worst spinal occlusion occurs at the place where the most pressure compresses the spinal cord. Despite the prospect of catastrophic injury occurring from burst fractures in the spinal region evidence shows that the spinal canal has the capability to reabsorb intracanal bony fragments in order to help clear the spinal canal. It would appear that this occurs regardless of whether spinal fixation is attempted or not.

Despite this natural clearance technique the body is equipped with, patients who clearly have neurological complications have been shown to be significantly better off following spinal fixation. This has been shown to assist them with earlier mobilization, improved pulmonary function and much greater relief from pain. The prime reason for spinal fixation is to reduce compression on the nerve roots and spinal canal, as well as realign the spine. Surgery is also effective in reducing the incidence of kyphotic deformity as well as increasing the stability, in the long term, for vertebral segments that has suffered trauma.

Certain surgery will be performed in injuries that reveal progressive neurological deterioration, as well as spinal canal compromise in excess of 50%, anterior vertebral body height loss in excess of 50%; incomplete neurological injury; kyphotic deformity of more than 25o – 35o angle; as well as an assortment of contiguous vertebral injury and trauma.

Proposed Treatment Algorithm

A new classification has been proposed by the Spine Trauma Study Group as a treatment algorithm for patients who have experienced thorocolumbar fractures. This algorithm is known as the Thoracolumbar Injury Classification and Severity Score, or TLICSS. It refers to the importance of three types of criteria that need to be considered to establish stability and decide on whether to resort to surgery or rely on conservative treatment. The TLICSS criteria are:

Morphology of the fracture:

1 point – compression

3 points – translational/rotational

4 points – distraction

Neurological Injury:

0 points – intact

2 points – nerve root injury

2 points – cord or conus medularis incomplete injury

3 points – cord or conus medularis complete injury

3 points – cauda equina syndrome

Integrity Status of Posterior Ligamentous Complex:

0 points – intact

2 points – injury suspected/indeterminate

3 points – injured

Total Score: this score measures from 1 – 10 points

For surgery to be considered necessary the criteria needs to exhibit 5 points or less

Non-surgical treatment will be provided when the criteria measures at 3 points or more.

Who is Unsuitable for Spinal Fixation?

Clinicians are far more selective about who undergoes spinal fixation nowadays. Too often in the past spinal fixation was carried out as a remedy for generic lower back pain. Without suitably advanced imaging techniques to prove otherwise, patients were operated on in an attempt to eradicate severe back pain for which no cure could be established. Nowadays, full imaging results are acquired to establish the need for spinal fixation, without which spinal fixation is not carried out. Patients with degenerative disc disease are not considered suitable candidates for spinal fixation and only very rarely is lower back pain treated with spinal fixation.

Devices Used for Spinal Fixation

So many unwarranted misconceptions abound when it comes to spinal fixation that people are understandably concerned about the prospect of having to face such surgery. Obviously, the best way to dispel such concerns is to discuss the various procedures in detail and to investigate who would best benefit from such procedures as well as what patients, having had spinal fixation carried out, can expect from it, as well as how this surgery is likely to affect their lives. Devices to enhance spinal stabilization are used in all areas of the spine, including the cervical, thoracic and lumbar regions.

Basically, a device used for spinal fixation needs to stabilize the posterior spine while limiting compression and enabling the maximum amount of movement. Generically, a spinal fixation device offers a permanent support that is either rigid or semi-rigid. The prosthesis itself is usually made from titanium. They include plates, rods, and screws, any of which could be incorporated into a device to fix an unstable spine. Another fixation device that is used in some instances is the resorbable fixation device made from a bio-resorbable substance such as one of the polymer products. If this is used there needs to be a device to prevent any acid damage occurring that might damage bone near the fixation device.There are various stabilizing techniques that are currently used, all of which are intended to provide additional stability for the posterior aspect of the spine. Most often, nowadays, spinal fixation is the preferred route although in a worst case scenario, spinal fusion is still an option. Spinal fixation is preferred as it tends not to limit range of movement.

The Generic Surgical Procedure for Spinal Fixation

There are all sorts of techniques that are used to undertake surgery for the fixation of the spine. Nowadays, any good surgeon will operate using the least invasive route possible. However, the ultimate outcome has to be the welfare of the patient and the success of the operation. The surgeon is trained to make these decisions on your behalf. First and foremost, minimally invasive surgery really relates to the amount of retraction needed by the surgeon to access the site of the operation to be able to carry out the repair that needs doing. If, during this time, he is able to use some of the newest tools available such as laser techniques then that is what the surgeon will do. However, the surgeon will advise you beforehand what he intends to do. What the surgeon actually does is totally dependent upon what he sees once you are under anesthetic and the surgeon can see the damaged area. The surgeon will then make a decision based on his knowledge, skills and experience, on the best way to complete the surgery successfully.

Expectations from Spinal Fixation

Invariably, patients will be able to resume their normal daily activities within a couple of months following spinal fixation surgery. Patients will notice that, following this surgery, they are largely free of pain, encouraging them to resume their lives where they left off prior to spinal problems preventing them living their lives to the fullest.

Anatomy of the spine

The Human spine extends from the skull to the pelvis and is made up of 33 individual bones termed vertebrae. The strong connective tissue act as a cushion between each vertebra, which holds one vertebra to the next. The disc allows the movement of the vertebrae and lets people bend and rotate their neck and back. The type and degree of motion varies between the different levels of the spine: cervical (neck), thoracic (chest) or lumbar (low back).

The cervical spine is a highly mobile region that permits movement in all directions.

The thoracic spine is much more rigid due to the presence of ribs and is designed to protect the heart and lungs.

Lumbar fusion

Lumbar fusion is a surgical technique in which two or more bones or vertebrae in the lower back are fused together. It is usually performed on patients who have chronic low back pain. It is also called a “spine fusion

Artificial Disc Replacement

Overview

Lost days of work, high cost of healthcare and one of the most common reasons for visiting the doctor: these are just some of the effects on the nations of the world from pain felt along the length of our spinal column, otherwise known as the vertebral column. Invariably, at one time or another during our adult lives, a huge number of us will suffer from back pain, often severe enough to be quite debilitating. In fact, statistics reveal that back pain will affect as many as 80% of us during our adult lives. The figure is revealed as 50% of adults for people suffering similar levels of debilitation as the result of neck pain. Back and neck pain both need to be taken seriously as each, in their own area of the vertebral column can give rise to serious disability, depending on the cause of the actual pain experienced.

Prior to the introduction of an acceptable design for the artificial disc replacement prosthesis in the USA during October 2004 and in Europe from 1993, more than 200,000 back pain sufferers every year underwent spinal fusion surgery. While not ideal, this was all that was available until artificial disc replacement became a viable alternative. Operations involving the artificial disc replacement prosthesis are highly successful, enabling patients to resume most of their previous activities with considerably reduced pain on movement.

Causes of Pain in the Vertebral Column

There are many, and various, conditions that can cause pain in different regions of the back, some of which are not even directly related to the spine itself. However, this would best be dealt with in more detail as a separate issue. Suffice to say, for the purposes of artificial disc replacement surgery, much of the pain experienced can be quite excruciating and severe enough to cause major and on-going disability, often as the result of the process of degeneration of the bones that make up the spine and, most likely actual degeneration of the inter-vertebral discs, those cushions that are interspersed between each vertebral bone. The diagram to the left shows healthy vertebrae, interspersed with healthy discs.

Discs Can Rupture due to Degeneration

A ruptured disc is sometimes called a herniated disc. However, despite the two different names, they both mean the same thing and the names are inter-changeable. In terms of spinal conditions, bulging discs are remarkably common although that is not to say that a bulging disc will inevitably go on to become herniated. Each of our vertebral discs is surrounded by a ligament and, if the center of the disc is pushed outwards towards the ligament, this results in a bulging disc. Quite often you can have a bulging disc and not know about it, only finding out about it if you need to have MRI investigation for another reason. However, if the disc bulges into the space reserved for the spinal canal this becomes cause for concern.

Structure of the Spine and Discs

Our spine is, quite literally, the backbone of our bodies, giving us structure and shape and providing the necessary support for all the other muscles, bones, tendons and ligaments to attach to. The spine is made up of a series of individual bones, each one interspersed with discs to prevent friction and act as shock absorbers, as well as enable greater flexibility and movement of the spinal bones when working in conjunction with each other. Facet joints are especially important for this to occur efficiently.

Discs consist of two distinct parts. The annulus fibrosus, or outer portion, as the name suggests, consists of a tough fibrous layer that encases the inner jelly. This outer layer of disc is in direct contact with nerve fibers, as well as pain receptors known as nocioceptors. The nucleus pulposus, otherwise known as the inner part, consists of jelly-like material made up of water and various proteins. During the normal aging process, as the discs degenerate, they begin to lose some of that water which can cause them to flatten out slightly. The fibrous layer can become slightly more brittle and give rise to cracks or tears, allowing the inner substance to leak out. The cracks and tears themselves can cause pain but, mostly these degenerative discs only cause pain if the leaking inner material presses up against the nocioceptors. This kind of back pain is known as discogenic low back pain.

Eventually, as degeneration continues, more water is lost, reducing their cushioning abilities, eventually causing more tears on the fibrous casing, finally resulting in the disc collapsing completely and causing the space between the vertebra to narrow, causing a shift of the facet joints that are the actual joints holding each separate bone together. This resultant change of position puts additional pressure on each facet joint causing additional problems to occur. If no treatment is provided osteophytes, also known as 'boney spurs' can develop around the facet joints and around the disc space.

Symptoms and Diagnosis

People usually experience quite severe pain in the back, often radiating to the buttocks and upper thighs. When the neck is involved the pain tends to radiate across the shoulders and over the shoulder blades, often into one or other of the arms. However, since there are so many conditions that can result in pain in the back or pain in the neck, your doctor will need to take a full history and complete some extensive examinations and tests. This will include a range of diagnostic tests, including X-rays and an MRI scan.

These will show up physiological changes such as bone spurs, altered position of vertebrae, or enlargement of the facet joint, also referred to as facet hypertrophy. Diagnostic tests also reveal instability on movement. An MRI scan is particularly useful to show where a disc might have lost water, where facet joint hypertrophy could exist, whether there is any stenosis or if one of the discs has herniated.

When would an Individual Consider Artificial Disc Replacement?

Most people who suffer with back pain respond well to non-surgical methods of treatment, what doctors refer to as 'conservative' treatment. However, if the back pain begins to interfere with daily activities that are affecting your quality of life and conservative efforts to treat you are not having much effect, then it may be necessary to consider surgery. Overall, and certainly until recently, surgery involved spinal fusion. This has been found to be successful in between 75% – 80% of patients but, quite often, these surgical interventions that involved fusion of the spine failed to heal sufficiently to completely eradicate back and neck pain as well as leaving patients with limited movement in the spine.

They have developed the most successful model based on two metal plates, each with teeth to implant it between the bones and a polyethylene core to enable cushioning and reduce friction. The design is completed with a metal ring that surrounds the whole prosthesis, enabling it to be picked up by X-ray. This artificial disc is known as the LINK SB Charite III.

The diagram above shows the Charite Artificial Disc that has been approved by the FDA for use in just one area of the lumbar spine, between bones L4 – S1, and only for patients who are suffering from degenerative disc disease that has not responded to conservative treatment after a minimum treatment over a period of 6 months. The Charite Artificial Disc is manufactured in Raynham, Massachussetts, USA by DePuy Spine Inc.

Artificial Disc Replacement is not Suitable for all Candidates

Candidates considered suitable for this kind of surgery are very carefully vetted and not all are found to be suitable for artificial disc replacement. As mentioned above, the FDA has approved one specific prosthesis for use between the 4th lumbar vertebrae and the 1st sacral vertebrae – and then only for patients whose condition hasn't responded to treatment after at least six months' continuous, non-invasive treatment. Furthermore, some patients may not be considered suitable due to their bones not being considered strong enough to support the prosthesis, perhaps due to the aging process.

Once inserted the artificial disc replacement tends to move and settle into position, making it unsuitable for patients who already have a vertebral slippage, otherwise known as spondylolisthesis, in excess of 3mm. At present, following clinical consultations, the most suitable candidates for artificial disc replacement fall into two categories:

Those with degenerative disc diseaseThose with post-discectomy syndrome

Discectomy syndrome refers to pervasive and persistent pain that patients continue to suffer following surgery to remove a disc that has ruptured.

What are the Different Kinds of Artificial Disc Replacements Used?

The FDA in the US approves this artificial disc replacement for use. It was developed by Professor Karin Buttner-Janz and Professor Kurt Schellnack, specialists in spinal surgery, in Berlin, Germany during the 1980s. This was the very first artificial disc replacement prosthesis. Although the original design was made by Waldemar Link GmbH in Europe, the design was purchased by the DePuy Group in 2003 and further modified before being acknowledged by the FDA as suitable for use in patients following extensive consultation and trials.

Worldwide, more than 15,000 patients have been treated successfully using the Charite artificial disc replacement, having been used in Europe for surgery for more than 17 years. The FDA approved the Charite for used in a certain sector of patients in October 2004, since then thousands of patients have been successfully treated with an artificial disc replacement.

Pre-Surgery Preparation

You will be evaluated as being suitable for surgery by the surgeon performing your operation. It is particularly important to advise your surgeon about your medication if you are a diabetic so that your condition can be monitored during surgery. The stress of the surgery on your body is likely to destabilize you, even if your diabetes is usually well under control so, continue to monitor your glucose levels more frequently for a few weeks following surgery, as well as prior to your operation. An anesthesiologist will also evaluate you to ensure that you are suitable for general anesthetic. To ensure there is as little risk as possible to you during and immediately after your operation you will be advised to consider making some small alterations to your lifestyle. This will minimize any risk factors and help your body to recover from the stress of surgery.

What Happens on the Day of the Surgery?

You will be asked to arrive at the hospital very early in the morning on the day of your operation, having had nothing to eat from midnight the night before. If you are going to be included in the morning operating list some surgeons prefer that you have nothing to eat or drink from 10pm the previous night.

You will be taken down to the operating room and administered a general anesthetic before being wheeled into the operating room. The only real difference between artificial disc replacement in the cervical vertebrae and those in the lumbar vertebrae is that the operation for the lumbar ADR is an anterior presentation. In other words, you will be lying on your back in the operating room and your operation will take place through your abdomen.

For this surgery there will be two surgeons present, a vascular surgeon and a general surgeon. The artificial disc replacement is placed in position through an incision in your tummy. The surgeon will move your internal organs to one side to gain access to the spine. This operation is much more straightforward done from the front as the surgeons can see better what is damaged and how much of your spine needs to be removed. The surgeon, wearing a surgical microscope, then spreads the vertebral bones widely apart to gain access to the damaged disc, making sure to remove as much damaged tissue as possible, taking special care to remove any tissue pressing against any of the nerves. Any osteophytes the surgeon comes across will also be removed. A special surgical device then separates the two adjacent bones – a bit like jacking up a car! The surgeon then uses a fluoroscope, which is a kind of X-ray, to place the artificial prosthesis in the correct space that has been prepared to take the new artificial disc replacement. Still relying on the view from the fluoroscope the surgeon then moves the vertebrae attached to the artificial devise to ensure that the ADR has been inserted correctly and all the pressure has been removed from the surrounding nerves.

The final step is to take an X-ray just to ensure everything is in the correct position, after which the surgery is completed with stitching up the various layers with different layered stitching, then stitching or clamping the skin together so that it gets to heal with the minimum of scar tissue.

What Happens After Surgery

Immediately post-operatively you will have intravenous lines in place and usually a urinary catheter. Both of these are usually removed by the second day. You will usually find that you are given IV antibiotics for the first 24 hours in order to prevent any immediate post-operative infection developing. The IV line is also used to provide you with adequate pain relief during the first couple of days: intravenous pain relief acts much faster than medication by any other route, as well as acting much faster, providing you with the most effective form of pain relief at a time when you need it most. Achieving the most appropriate level of comfort immediately post-operatively is an important part of your rehabilitation process so, if you do experience an unacceptable level of pain, contact the nursing staff and let them know. Only you can know how much pain is acceptable to you and how much pain you are prepared to cope with!

Rehabilitation

For most people their stay in hospital, following surgery, lasts for around 3 – 4 days and is usually accompanied with an increasing awareness that their previously painful symptoms are improving. This gradual improvement continues over the subsequent weeks, with most people gradually being able to completely tail-off all their medication eventually. Some people find they may need an extra couple of days in hospital, depending on the degree of pain. The hospital staff is aware that everybody recovers at a different rate and experience different levels of pain, so there is no pressure on you to leave hospital before you feel ready. Many people find they are able to get up and walk around within hours of their operation.

If you are able to do so this is much better for you as it will reduce the possibility of complications such as DVT or embolism developing. As long as you are careful how you move gentle exercise is encouraged and, on your return home you should be able to carry out your normal activities quite soon. One of the advantages of ADR is that you are unlikely to need any back support during the healing period and can get back to driving a car or cycling quite quickly although you are advised not to lift more than about 10lbs for up to a month or so after surgery. It is important, however, that you let your body heal at its own rate and don't attempt to do too much too soon.

During your post-operative period you will continue to be followed up by your surgeon, with subsequent X-rays to check everything is healing properly. You need to follow your surgeon's advice about how soon you can return to work although this is largely dependent on the kind of work you do. In general, however, you will usually be advised that you should be fit enough to return to sporting activities by about the 13th week following surgery.

Risks Associated with Artificial Disc Replacement

There are risks associated with any surgery, but with good management and co-operation on your part prior to surgery, these can be minimized considerably. The most obvious risks associated with ADR, apart from the usual surgical risks are:

The metal plate breakingThe implant dislocating out of the jointInfection surrounding the prosthesis

Aside from that, there is the usual risk of developing DVT and, those in the higher risk category will be offered daily injections of Lovenox or, orally, Coumadin can be prescribed. The other problem that can occur is a dural tear, although this is usually noted during surgery and repaired. If it develops later it can cause quite severe headaches and infection but usually the leaking dura will close itself off through your body's own healing process. The worst case scenario, if it doesn't heal on its own accord, is a second operation to heal the breach in the dura.Overall, most patients who undergo surgery for ADR resume their normal daily occupations quite quickly and, while nobody likes the prospect of surgery, the operation to fit an artificial disc in place of damaged tissue is usually a very safe procedure that offers excellent results to thousands of people who would, otherwise be severely debilitated. While still regarded as a new procedure, the insertion of artificial disc prosthesis is a vast improvement on the only other option which was spinal fusion; nowhere near as effective or successful as ADR is promising to be.